The invention relates to a multiwire unit particularly for a medical instrument, and to a method of producing such a multiwire unit.
Multiwire units of this type are used, for example, as wire basket units, which may also be called wire cage or catching basket units, for medical instruments for catching and removing stones or other concretions from human or animal tissue canals. In the present context, the term “wire basket” means that several wire sections are arranged around a longitudinal axis of the wire basket unit at a distance from one another extending essentially axially in the circumferential direction. In a basket-forming condition, they extend from a forward end area of the wire basket unit, while forming the wire basket, first expanding radially toward the outside and then narrowing again radially toward the inside. The wire sections consist of a sufficiently elastic, not necessarily metallic material, frequently superelastic metal alloys being used.
Typically, the wire sections are guided in a rearward end area through a receiving sleeve into which they can be pulled while the wire basket shrinks radially. In the pulled-out basket-forming condition, a stone or the like can move into the widened wire basket through the spaces between the wire sections, after which, by a pulling of the wire sections into the receiving sleeve, the wire basket is drawn together and the stone can be retained for the removal.
Medical instruments of this type are used in various designs, for example, as endoscopes, such as stone catching basket instruments and balloon catheter instruments. For this and other applications, a forward end closure of the wire basket which is as short of possible is frequently desirable. In constructions, as disclosed, for example, in U.S. Patent Document U.S. Pat. No. 6,013,086, the forward wire section ends or forward end bows of wire loops are held in a cylindrical end sleeve which therefore remains disposed in front of the actual wire basket area.
German Published Patent Application DE 197 22 429 A1 discloses a device for catching and/or crushing objects in hollow organs, particularly gallstones or kidney stones, which is constructed as a multiwire unit of the above-mentioned type; that is, it contains several wire sections, which are formed in one piece from a tubular piece whose tubular jacket is subdivided in an axial partial area into the wire sections by several axial slots spaced in the circumferential direction. In this case, the wire sections remain mutually linked at a forward end area in that the axial slots end there while leaving a forward wire linkage area at a distance in front of a forward tube front end, and in a predefinable functional state of the multiwire unit following the wire linkage area, assume a bent small-basket forming functional state. In the case of this known multiwire unit, the axial slots end at a relatively large distance in front of the forward tube front end, so that a tip-forming forward end stub of the tubular piece remains which forms the wire linkage area. The distance of the axial slots from the forward tube front end is clearly greater than the diameter of the tubular piece and the width as well as the thickness of the wire sections. The tubular piece, which consists, for example, of nickel titanium wire and has the inserted wire sections, is used as a pull cord of this catching basket device. The axial slots are made, for example, by laser beam cutting. The forward tip end of the catching device may be equipped with a hemispherical end element and/or with a bordering ring visible by x-ray.
In contrast, so-called “tipless” wire basket units have been suggested. Thus, International Published Patent Application WO 98/36694 A1 describes wire basket units, where the basket-forming wire bows on the forward wire basket end, while forming narrower loops, are mutually linked loosely and thereby in an articulated manner. In German Patent Document DE 101 17 836 C1, it is suggested that the wire sections be held at the forward end in an articulated manner on a fixing body which may be designed such that, in the basket-forming condition, a virtually tipless forward end of the wire basket unit is obtained.
Furthermore, multiwire units are also used in medical instruments as wire filters, such as coronary filters, for catching deposits or clumping in tissue ducts, for example, for preventing emboli.
The invention is based on the technical problem of providing a multiwire unit of the initially mentioned type, which can be implemented in a tipless manner at comparatively low expenditures, and of providing a pertaining production method.
The multiwire unit according to the invention can be formed in one piece from a tubular piece in that several axial slots spaced in the circumferential direction are placed in its tubular jacket, which axial slots, while leaving a wire linkage area, end at a distance in front of a tube front end. As a result, the tubular jacket is divided into several wire sections which, in a section adjoining the wire linkage area, are bent to the shape desirable for a corresponding functional state of the multiwire unit, characteristically, the wire linkage area also deforming, so that an essentially tipless end closure is formed.
The invention therefore permits the production of a tipless multiwire unit made of only a single piece, that is, the tubular piece. The forward wire linkage area, by way of which the wire sections remain cohesively mutually connected at the forward end area, corresponding to the requirements, can be designed such that, when the wire sections are bent open or bent over correspondingly, for example, a virtually tipless wire basket or a virtually tipless wire filter with a desired maximal filtering width is obtained. For this purpose, the axial slots extend to a relatively narrow distance from the forward tube front end, so that, when the wire sections are bent open or over, the wire linkage area is also deformed and no noticeable axial tubular piece end stub remains; that is, in its functional state, the multiwire unit ends essentially in a tipless manner in that also the wire linkage area itself bends while the material is deformed.
As a person skilled in the art will understand, the term tipless indicates a forward end closure design of the multiwire unit which either has no axial end stub originating from the basic tubular piece or has only a very small end stub whose dimensioning and particularly whose axial length is negligibly small in comparison to the dimensions of the adjoining functional part formed by the wire sections, such as a wire basket or a wire filter; for example, only has an axial length which is by one or more orders of magnitude smaller than the maximal diameter of an adjoining wire basket. In particular, the term “tipless” or “essentially tipless” means that no remaining axial end stub projects abruptly toward the front from the adjoining functional unit formed by the wire sections, but the multiwire unit changes as early as from its forward end in a course bent open with respect to the tubular piece blank from the wire linkage area into the bent course of the wire sections in the functional unit.
In an advantageous embodiment of the invention, the tubular piece and thus the multiwire unit consists of a superelastic material. As a rule, such materials also have a shape memory. The latter can be utilized for selecting the functional state of the wire sections as the dimensionally stable state, so that the wire sections assume their functional state on their own when they are not prevented therefrom by outside forces, for example, by a sliding into a receiving sleeve, or are changed into a different state.
In a further development of the invention, the wire sections at the wire linkage area are bent by at least approximately 60°, as required by approximately 90° or more, relative to their axial tubular jacket position into the functional state. Thus, for example, a bending-open by approximately 90° permits the implementation of a completely bluntly ending wire basket which, at the forward end, with an at most slight axial component, expands essentially radially toward the outside, which is frequently desirable particularly for medical instruments, or of a wire filter which can also be used in medical instruments. For providing corresponding multiwire units, a bending-over of the wire sections by more than 90° may also be provided; that is, virtually, at least in areas, a turning-over of the tubular piece divided into the wire sections.
An embodiment of the invention provides an advantageous flexibility of the wire linkage area for forming the functional state of the multiwire unit in that the axial distance of the axial slots from the forward tube front end is selected to be smaller than an outside diameter and/or an inside diameter and/or to be approximately equally large as a or smaller than a wall thickness of the tubular piece and/or approximately equally large as or smaller than a width of the wire sections. Depending on the concrete other shaping of the wire linkage area, this permits a deforming of the end-side wire linkage area such that no noticeable axial end stub of the tubular piece remains; that is, a tipless end closure of the multiwire unit is achieved in a desired shaping of the wire linkage area.
In an advantageous embodiment of the invention, one or more slot-shaped recesses are placed in the tubular jacket from the front side of the tubular piece or adjacent thereto, which slot-shaped recesses are situated in the circumferential direction of the tubular piece at angular positions between the angular positions of the axial slots. By means of these slot-shaped recesses, the bending behavior of the wire sections in the wire linkage area and the shape of the wire linkage area in the functional state of the multiwire unit can be influenced in the respectively desired manner.
In an advantageous further development, the slot-shaped recesses extend axially into the area between the axial slots. In a further development, the axial slots are tapered in their area overlapping with the slot-shaped recesses; that is, they have a smaller width there than in their rearward portion outside this overlapping area. Advantageous shapes of the axial slots and of the slot-shaped recesses in the overlapping area are, for example, those with an essentially uniform width of the axial slots and of the slot-shaped recesses or those with axial slots oppositely tapering in a wedge-shaped manner and with slot-shaped recesses. Another advantageous shaping variant provides several rows of slot-shaped recesses following one another in the circumferential direction, these rows being offset in the axial direction and axially overlapping or not overlapping with one another.
In a further advantageous development of the invention, the tube front end is provided with an outer surrounding profiling, such as a wave-shaped profile. Also this measure can influence the shape of the wire linkage area in the functional state of the multiwire unit as well as the bending behavior of the wire sections in this area in a desired manner.
Objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.